Here's a potential falsification that I tried on another message board:
Suppose that God did
not create the light in between the stars and the earth like the creationists insist? Then throughout history, "new" stars would have continually come into view as the light from those stars would finally have time to reach earth.
Imagine, that we could only see the stars out to 6000 light years or so, and every year astronomers would discover new stars as the sphere of the visible universe comes into view, one light-year at a time....
That would be some pretty powerful evidence of a young universe.